1. Field of the Invention
The present invention relates to the use of industrial controllers for monitoring and reporting the status of industrial equipment.
2. Background Art
Industrial equipment is used to manufacture or process a wide variety of products, raw materials, intermediate components, and the like. Industrial equipment may also provide a variety of services such as cleaning, packaging, weighing, counting, forming, coating, and the like. Typically, industrial equipment is operated under the control of one or more industrial controllers. Industrial controllers allow the operation of the industrial equipment to be programmed by one or more of the equipment manufacturer, system integrator, plant engineer, and the like. Programmable industrial control can be implemented in special purpose hardware such as robotic controllers, proprietary processors, and the like. Industrial controls may also be implemented in more general hardware such as programmable logic controllers (PLC), personal computers, and the like.
Industrial controllers generate control signals based, in part, on detecting an event or state in the controlled machine. Typically, the industrial controller receives input from sensors monitoring the operation of the industrial equipment. In addition to generating control signals, industrial controllers have been programmed to display or output as data information about the condition of controlled equipment. Recently, central computer systems have been networked to industrial controllers for collecting status information. This information has been aggregated and displayed to provide an indication of plant-wide operations.
Several problems exist with current industrial control monitoring systems. First, each industrial controller is typically programmed with custom software for generating and transmitting status information. This software may take the form of an interrupt or other anomaly handling process which generates and transmits an event message when a specified event occurs. This typically requires that the industrial controller contain complex and individualized logic for anomaly handling.
A second problem with existing systems results from the unpredictable and uncontrolled nature of messages generated and transmitted by the industrial controllers. Each controller generates messages as the need arises. Hence, there is no centralized control of communication network resources. This may result in wasted network bandwidth and network clogging during critical situations.
Third, precise and accurate time stamping of status messages is often necessary to accurately determine the root cause of a manufacturing problem in a complex process including multiple pieces of manufacturing equipment. Systems that time stamp messages upon receipt at a centralized computer system or when the message is sent from the industrial controller create timing inaccuracies making accurate cause-and-effect analysis difficult.
Fourth, many industrial controllers have limited processing and memory resources. These limited resources prohibit the implementation of complex network signaling techniques.
What is needed is to log industrial equipment events in a manner which utilizes a low amount of system resources, is simple and robust, allows for a high degree of synchronization between industrial controllers, and has a high degree of uniformity amongst similar industrial controllers.